A phase varying apparatus for an automobile engine adapted to vary the phase angle between the crankshaft and camshaft of the engine to vary valve timing is disclosed in Patent Document 1 cited below. This Patent Document 1 has a camshaft a drive rotor driven by the crankshaft and rotatably mounted on a center shaft which is integral with the camshaft, a first and a second control rotor rotatably mounted on a center shaft, a first and a second electromagnetic clutch for putting a brake on the first and the second control rotor, respectively.
The first control rotor can rotate in the phase retarding direction relative to the camshaft as it is braked by the first electromagnetic clutch. Consequently, a first intermediate rotor and a shaft member, mounted on the center shaft are moved in the radial direction of a second intermediate rotor. The first intermediate rotor is mounted on the center shaft unrotatably relative thereto but moveable in the direction perpendicular to the axis of the center shaft. The shaft member, moveable in the radial direction of the second intermediate rotor, can move in a guide groove that has a shrinking radius formed in a drive cylinder to thereby rotate the first intermediate rotor and the center shaft relative to the drive rotor. As a result, the phase angle of the camshaft relative to the drive rotor is altered either in the phase advancing direction D1 or phase retarding direction D2.
On the other hand, provided between the front end of the first control rotor and the second control rotor is the second intermediate rotor, which has a guide groove extending substantially in the radial direction (the groove hereinafter referred to as radial groove) and is fixedly secured to the center shaft. Formed in the front end of the first control rotor and in the rear end of the second control rotor are eccentric circular holes, respectively, in which, and across the second intermediate rotor, a second and a first ring member are engaged respectively. The second and first ring members are connected to the opposite ends of the shaft member which is passed through the radial guide groove. The second control rotor, when subjected to a braking force of the second electromagnetic clutch, rotates the second ring member in the eccentric circular hole and displaces the shaft member in the radial guide. The displaced shaft member causes the first ring member to rotates in the eccentric circular hole, which in turn causes the first control rotor to rotate in the phase advancing direction relative to the drive rotor. Consequently, by energization of the second electromagnetic clutch, the phase angle of the camshaft relative to the drive rotor is varied in the opposite sense as compared with the phase angular variation caused by energization of the first electromagnetic clutch.